The Latest on H1N1 Swine Flu

Such a concerted vaccination effort could lead to coverage of 70% of the
U.S. population, say researchers at the Fred Hutchinson Cancer Research
Center's Vaccine and Infectious Disease Institute.

Their analysis, aided by computer modeling, is published in the Sept. 11
issue of Science Express, an early online edition of the journal
Science.

The study recommends that 70% of children between 6 months and 18 years old
be vaccinated first in such a program, along with members of other high-risk
groups, including health care workers and people with chronic medical
problems.

The researchers say two doses of vaccine, administered three weeks apart,
may provide enough protection against the virus.

A combination of factors, including the availability of an effective vaccine
and the timing of an outbreak, will determine how quickly an epidemic can be
slowed, according to co-author Ira Longini Jr., PhD, of the Fred Hutchinson Cancer Research Center and the University of Washington.

"Our estimates of pandemic H1N1 in households, schools, and in the
community places this virus in the higher range of transmissibility,” lead
author Yang Yang, PhD, of the Fred Hutchinson Cancer Research Center and the
University of Washington, says in a news release.

The report also estimates that:

Children are likely to experience the highest illness attack rates.

The typical student will infect an average of 2.4 school mates.

30%-40% of flu transmission occurs in households, about 20% in schools, and
the rest in the workplace and the community.

Pandemic spread may cause illness in 25%-29% of the world population in one
year, resembling what happened during the 1957-58 Asian influenza A (H2N2)
pandemic.

The average time between the onset of illness in a person and onset of
illness in someone that person infects may be 2-3 days.

H1N1 already has become the dominant flu strain in the Southern Hemisphere,
where flu season is under way. Vaccination increases immunity and slows spread
of infection, and reduces risk for flu complications and death.

The researchers also say that social distancing and antiviral medications
can be effective in offsetting spread of H1N1 when combined with vaccination on
a mass scale.

SOURCES: Annals of Internal Medicine, vol 149(9). News release, American College of Physicians. Ralf Nass, MD, professor of medicine, University of Virginia School of
Medicine. Michael Thorner, MB, BS, DSc, professor of medicine, University of Virginia
School of Medicine. Lawrence Phillips, MD, professor of medicine, Emory University School of
Medicine.